In current antenna designs, three improvement methods are used in the dual-band dual-port antenna structure for reducing mutual coupling between the low-band part and the high-band part of the dual-band dual-port antenna structure. The first improvement method is increasing the distance between the low-band part and the high-band part and it is a conventional means of reducing mutual coupling. It is easy to understand that the wider the distance between two parts, the smaller the mutual coupling that can be obtained. The disadvantage is clear because it would cause the antenna structure to be less compact and space-consuming. The second improvement method is employing a decoupling structure between the low-band part and high-band part of the dual-band dual-port antenna structure. The decoupling structure in the second improvement method includes shorting the post/strip/patch, the decoupling networks, the electromagnetic band-gap (EBG) structure, and so on. This technique can improve the mutual coupling in a relatively small space compared with the first method, but it still needs a certain structure between the low-band and high-band parts, which makes the total structure relatively complicated. Moreover, such techniques are usually narrow-banded. The third improved method is orthogonal polarization. The third improvement method makes the polarization of two bands orthogonal with each other, which is an effective way to decrease the mutual coupling. However, this method is special and it cannot meet the requirements on systems where the same polarization at both bands is required.